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Ask HN: Are there any projects to do historical archiving of RF spectrum?

by adamgamble on 7/28/16, 7:38 PM with 25 comments

• by kastnerkyle on 7/29/16, 1:15 AM

  As vitovito mentions, wideband data in high resolution is incredibly expensive from a storage perspective. There are entities that do it, but this also has the same privacy concerns as saving every packet that comes over a wire - in fact if you record 2.4 MHz and 5 MHz you will be picking up someone's (hopefully encrypted) private data. I don't think it is illegal, but the technical aspects of this are pretty daunting.

  You would be better off decoding and storing that, but that gets into v& territory pretty quickly, depending on who and what you decode (definitely don't decrypt/crack).

• by pigeons on 7/28/16, 8:26 PM

  Hard enough to get good coverage, and very hard to get the storage resources. There was a CCC talk about setting up coverage, but that was ambitious enough, archiving was mostly out of scope:

  http://www.cw-complex.com/rfarray/

  http://www.rtl-sdr.com/talk-monitoring-spectrum-building-dis...

• by derptacious on 7/28/16, 10:07 PM

  This is super interesting! And if anyone else is curious about creating a project that monitors the range of RF amplitude and frequency at many data points around the world, then send me your contact info! I want to see a record of this spectrum (human and non-human made) in frequency and amplitude to see how much it is (and hopefully "has") changed in physical space. I think interesting things would come out of this data.

• by vitovito on 7/28/16, 9:06 PM

  From my notes on a radio archiving project I'm doing:

  > Could you record the entire radio spectrum and extract stations and broadcasts later?

  > In the USA, the AM radio band is 540-1710 kHz, a spread of 1170 kHZ,

  > http://rtl-sdr.better-than.tv/?page_id=237 states that spectrum recordings are also a function of how many samples per second you choose to record:

  > 2.8msps - 44.8mbps = 5.6 MB/sec.

  > 2msps - 32mbps = 4 MB/sec.

  > 1msps - 16mbps 2 MB/sec.

  > http://www.myradiobase.de/perseus/ has sample files. 3.5 minutes is ~360MB. 60 seconds of 1500 kHZ is a gig. All too much. 24 hours at 1MB/min is 1.5GB, but 17MB/sec. is 1.4TB. Spectrum recordings are out.

• by jf on 7/28/16, 10:46 PM

  The Internet Archive is archiving some of the broadcast TV part of the RF spectrum, which is where this comes from: https://archive.org/details/tv

• by privong on 7/29/16, 3:03 PM

  Most of the major radio astronomy observatories maintain archives (e.g., [0]). Of course, they mostly use highly directional dishes pointed at the sky, but local radio signals can create interference[1]. So, those archives provide some probe/record of terrestrial RF spectrum. Of course, those telescopes are generally placed in radio-quiet locations.

  [0] https://archive.nrao.edu/archive/advquery.jsp

  [1] http://www.gb.nrao.edu/IPG/

• by gravypod on 7/29/16, 3:57 AM

  Archiving the entire spectrum can range anywhere from infeasible to impossible. First you'd need to specify the frequency ranges you want to listen to.

  Then you've got a data storage problem which has been covered.

  After that you've got the propagation problem. Not everything is seen from everywhere.

  In any event you might want to check out http://www.reversebeacon.net/

  It's a project that's got a different "simpler" archiving goal. It is just to track spots of people calling CQ in the CW bands.

• by vesche on 7/28/16, 11:12 PM

  As vitovito and pigeons mentioned storage and collection locations are the main issues. Things like this exist, but they don't archive data and are designed for military use- Google: Wideband Recording System . They typically are mobile units that focus on fast capture rate and decently large storage (a few terabytes).

  sigidwiki is worth looking at, but it's more for classification: http://www.sigidwiki.com/wiki/Signal_Identification_Guide

• by superuser2 on 7/28/16, 10:53 PM

  >all the radio information as 9/11 transpired

  I know it's not everything, but if you are interested in this the New York Times has an excellent feature using the ATC tapes and some recorded phone lines in the military/air defense system.

  http://www.nytimes.com/interactive/2011/09/08/nyregion/911-t...

• by niftich on 7/28/16, 11:19 PM

  I find this fascinating because the context of transmissions occurring simultaneously is indeed ephemeral.

  This data gets lost with traditional archiving, which is squarely considers context (including temporal simultaneity across multiple objects) to be metadata.

  These sorts of efforts can be partially retrofitted/approximated with timecodes on existing archived material, which may also be a separate, worthwhile endeavor to pursue.

• by theknarf on 7/29/16, 12:22 PM

  The closest thing I know about is websdr (http://websdr.org)

• by barrystaes on 7/29/16, 10:40 AM

  Likely there are top-secret satellites doing exactly that for specific geographic regions. These likely wont retain all gathered data indefinitely however, and even if data is shared its tainted politically.

• by wyldfire on 7/28/16, 8:00 PM

  No but that sounds like a good idea!

• by rfw1z on 7/28/16, 8:23 PM

  there are commercial solutions that do this